Welcome! I'd be careful choosing breeds to mix with Silkies, and definitely get them at the same time, or have the standard birds a bit younger than the Silkies, not the other way.
In my experience, production reds, which include hatchery RIRs, tend to be aggressive with their flockmates, and could be a real threat to Silkies, who are smaller, cat's see well under that cute top knot, and are generally more fragile. Many people with Silkies have them in a separate coop, so be ready.
There are so many breeds and colors to choose! Have you looked at feathersite online, or the Cackle catalog, or Henderson's breed chart? So many choices!!!
Mary